1. Field of the Invention
The present invention relates to an image storage and display system, and more particularly to an image storage and display system having a workstation and an image server storing a plurality of medical image data connected via a network, for use in a medical network.
2. Description of the Related Art
There are in use in the medical field today apparatus (modalities) for forming X-ray and other diagnostic images used in a variety of diagnosis, including CR (computed Radiography) apparatus, CT (Computerized Tomography) apparatus, MRI (Medical Resonance Imagery) apparatus, etc. The image data produced in each modality is displayed on a CRT terminal (hereinafter referred to simply as a CRT), or output by a laser printer, etc. to film, etc. for use by a reader at a medical treatment site in ascertaining the presence or absence of a disease, tissue damage, etc.
In addition, recent advances in computer and communications technology have seen the deployment of medical network systems (hereinafter referred to simply as networks) in hospitals and other facilities. Therefore, whereas in the past the aforementioned modalities were used only on a stand-alone basis, now they are connected to a network as image input apparatus, and CRTs, laser printers, etc., as image output apparatus.
Aside from aforementioned image input and output apparatus, also connected to such a network is an image server equipped with recording means for recording image data output by the image output devices, as it is, or after it has been subjected to a predetermined data-compression process, to a storage medium such as a hard disk, a RAID (Random Array of Inexpensive Disks), an optical disk: CD-R, DVD, DLT (Digital Linear Tape); etc. Image data input to such an image server is temporarily recorded on a high output-speed temporary storage medium (referred to as a short-term storage medium) such as a hard disk or a RAID, and after the set conditions have been satisfied (such as the passage of a predetermined period of several weeks to several months after a doctor has completed diagnosis employing an image), the image data is compressed and recorded on a storage medium such as an optical disk, etc. (archive), for semi-permanent storage. This is because the price of the temporary storage medium is comparatively high, and therefore high costs are incurred in expanding the storage capacity thereof. Furthermore, data management of image data thus stored in the image server, such as transferring image data from a temporary storage medium to an archive, etc. is conducted by a database.
In such a network, predetermined image data is transmitted from the image server to a workstation connected to the network in response to a request from the workstation. In this way, it is possible to display at the workstation image data required for diagnosis. Further, because image data obtained by aforementioned input modalities is stored in a short-term storage medium before aforementioned set conditions are satisfied, it can be read out at a comparatively high speed; therefore, if there is a request from the workstation, the image data can be expeditiously transmitted to the workstation. In addition, not only the internal network of a hospital, but also a computer at a doctors residence, for example, can be connected via a communications circuit such as a telephone line to enable image data to be read out from the image server in order to carry out so-called remote diagnosis (teleradiology). However, compared to the dedicated lines composing the internal hospital network, data transmitted over aforementioned communications circuits is transmitted at a slower rate, and therefore the time required for downloading image data is longer. In order to improve transmission efficiency of diagnostic images to be utilized for remote diagnosis, it is proposed to provide for transmission of image data that has been determined in advanced to be the desired image data and which has been subjected to a comparatively high-rate data-compression process, and to provide notification upon completion of transmission, using the so-called push-style.
On the one hand, as a type of diagnosis, images obtained in the present are compared to images obtained in the past in a comparative diagnosis. When such comparative diagnosis is performed, it is necessary to acquire the past image data from the image server. Because image data stored in the short-term storage medium is transferred in the long-term storage medium after the set conditions have been satisfied, to acquire the past image data it is necessary to search for the past image data in the long-term storage medium, copy it to the short-term image medium and then transmit it to the workstation.
On the other hand, the so-called pre-fetch procedure in which the past image data is copied to the short-term storage medium in advance, according to an examination schedule, etc., is performed. However, for emergency cases, etc., if there is a request for past image data that is not in the schedule, in the same way described above, the past image data must be acquired by searching for it in the long-term storage medium, copying it to the short-term image medium and then transmitting it to the workstation.
Accordingly, it takes time for the past image data to be displayed at the workstation.
In addition, because aforementioned past image data is subjected to a comparatively high-rate data compression process, it is degraded in image quality compared to the original image data. However, high image-quality past image data is desired for use in carrying out comparative diagnosis. However, because the original image data is deleted after aforementioned set conditions have been satisfied, it has not been possible to view high image-quality images obtained in the past.
Further, for cases in which remote diagnosis is to be performed, because the communications circuit over which image data is transmitted has a low data-transmission rate, it is preferable that the compression ratio of such image data is high. However, only past image data is compressed at a high compression rate and stored, and when remote diagnosis is to be performed, the image data obtained in the present must be subjected to a data-compression process and then transmitted; therefore, long transmission times are required.